* Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> [250428 11:28]:
> There is functionality that overlaps the exec and memory mapping
> subsystems. While it properly belongs in mm, it is important that exec
> maintainers maintain oversight of this functionality correctly.
>
> We can establish both goals by adding a new mm/vma_exec.c file which
> contains these 'glue' functions, and have fs/exec.c import them.
>
> As a part of this change, to ensure that proper oversight is achieved, add
> the file to both the MEMORY MAPPING and EXEC & BINFMT API, ELF sections.
>
> scripts/get_maintainer.pl can correctly handle files in multiple entries
> and this neatly handles the cross-over.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> MAINTAINERS | 2 +
> fs/exec.c | 3 ++
> include/linux/mm.h | 1 -
> mm/Makefile | 2 +-
> mm/mmap.c | 83 ----------------------------
> mm/vma.h | 5 ++
> mm/vma_exec.c | 92 ++++++++++++++++++++++++++++++++
> tools/testing/vma/Makefile | 2 +-
> tools/testing/vma/vma.c | 1 +
> tools/testing/vma/vma_internal.h | 40 ++++++++++++++
> 10 files changed, 145 insertions(+), 86 deletions(-)
> create mode 100644 mm/vma_exec.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f5ee0390cdee..1ee1c22e6e36 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8830,6 +8830,7 @@ F: include/linux/elf.h
> F: include/uapi/linux/auxvec.h
> F: include/uapi/linux/binfmts.h
> F: include/uapi/linux/elf.h
> +F: mm/vma_exec.c
> F: tools/testing/selftests/exec/
> N: asm/elf.h
> N: binfmt
> @@ -15654,6 +15655,7 @@ F: mm/mremap.c
> F: mm/mseal.c
> F: mm/vma.c
> F: mm/vma.h
> +F: mm/vma_exec.c
> F: mm/vma_internal.h
> F: tools/testing/selftests/mm/merge.c
> F: tools/testing/vma/
> diff --git a/fs/exec.c b/fs/exec.c
> index 8e4ea5f1e64c..477bc3f2e966 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -78,6 +78,9 @@
>
> #include <trace/events/sched.h>
>
> +/* For vma exec functions. */
> +#include "../mm/internal.h"
> +
> static int bprm_creds_from_file(struct linux_binprm *bprm);
>
> int suid_dumpable = 0;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 21dd110b6655..4fc361df9ad7 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3223,7 +3223,6 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
> extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
> extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
> extern void exit_mmap(struct mm_struct *);
> -int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift);
> bool mmap_read_lock_maybe_expand(struct mm_struct *mm, struct vm_area_struct *vma,
> unsigned long addr, bool write);
>
> diff --git a/mm/Makefile b/mm/Makefile
> index 9d7e5b5bb694..15a901bb431a 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -37,7 +37,7 @@ mmu-y := nommu.o
> mmu-$(CONFIG_MMU) := highmem.o memory.o mincore.o \
> mlock.o mmap.o mmu_gather.o mprotect.o mremap.o \
> msync.o page_vma_mapped.o pagewalk.o \
> - pgtable-generic.o rmap.o vmalloc.o vma.o
> + pgtable-generic.o rmap.o vmalloc.o vma.o vma_exec.o
>
>
> ifdef CONFIG_CROSS_MEMORY_ATTACH
> diff --git a/mm/mmap.c b/mm/mmap.c
> index bd210aaf7ebd..1794bf6f4dc0 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1717,89 +1717,6 @@ static int __meminit init_reserve_notifier(void)
> }
> subsys_initcall(init_reserve_notifier);
>
> -/*
> - * Relocate a VMA downwards by shift bytes. There cannot be any VMAs between
> - * this VMA and its relocated range, which will now reside at [vma->vm_start -
> - * shift, vma->vm_end - shift).
> - *
> - * This function is almost certainly NOT what you want for anything other than
> - * early executable temporary stack relocation.
> - */
> -int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
> -{
> - /*
> - * The process proceeds as follows:
> - *
> - * 1) Use shift to calculate the new vma endpoints.
> - * 2) Extend vma to cover both the old and new ranges. This ensures the
> - * arguments passed to subsequent functions are consistent.
> - * 3) Move vma's page tables to the new range.
> - * 4) Free up any cleared pgd range.
> - * 5) Shrink the vma to cover only the new range.
> - */
> -
> - struct mm_struct *mm = vma->vm_mm;
> - unsigned long old_start = vma->vm_start;
> - unsigned long old_end = vma->vm_end;
> - unsigned long length = old_end - old_start;
> - unsigned long new_start = old_start - shift;
> - unsigned long new_end = old_end - shift;
> - VMA_ITERATOR(vmi, mm, new_start);
> - VMG_STATE(vmg, mm, &vmi, new_start, old_end, 0, vma->vm_pgoff);
> - struct vm_area_struct *next;
> - struct mmu_gather tlb;
> - PAGETABLE_MOVE(pmc, vma, vma, old_start, new_start, length);
> -
> - BUG_ON(new_start > new_end);
> -
> - /*
> - * ensure there are no vmas between where we want to go
> - * and where we are
> - */
> - if (vma != vma_next(&vmi))
> - return -EFAULT;
> -
> - vma_iter_prev_range(&vmi);
> - /*
> - * cover the whole range: [new_start, old_end)
> - */
> - vmg.middle = vma;
> - if (vma_expand(&vmg))
> - return -ENOMEM;
> -
> - /*
> - * move the page tables downwards, on failure we rely on
> - * process cleanup to remove whatever mess we made.
> - */
> - pmc.for_stack = true;
> - if (length != move_page_tables(&pmc))
> - return -ENOMEM;
> -
> - tlb_gather_mmu(&tlb, mm);
> - next = vma_next(&vmi);
> - if (new_end > old_start) {
> - /*
> - * when the old and new regions overlap clear from new_end.
> - */
> - free_pgd_range(&tlb, new_end, old_end, new_end,
> - next ? next->vm_start : USER_PGTABLES_CEILING);
> - } else {
> - /*
> - * otherwise, clean from old_start; this is done to not touch
> - * the address space in [new_end, old_start) some architectures
> - * have constraints on va-space that make this illegal (IA64) -
> - * for the others its just a little faster.
> - */
> - free_pgd_range(&tlb, old_start, old_end, new_end,
> - next ? next->vm_start : USER_PGTABLES_CEILING);
> - }
> - tlb_finish_mmu(&tlb);
> -
> - vma_prev(&vmi);
> - /* Shrink the vma to just the new range */
> - return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
> -}
> -
> #ifdef CONFIG_MMU
> /*
> * Obtain a read lock on mm->mmap_lock, if the specified address is below the
> diff --git a/mm/vma.h b/mm/vma.h
> index 149926e8a6d1..1ce3e18f01b7 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -548,4 +548,9 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address);
>
> int __vm_munmap(unsigned long start, size_t len, bool unlock);
>
> +/* vma_exec.h */
> +#ifdef CONFIG_MMU
> +int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift);
> +#endif
> +
> #endif /* __MM_VMA_H */
> diff --git a/mm/vma_exec.c b/mm/vma_exec.c
> new file mode 100644
> index 000000000000..6736ae37f748
> --- /dev/null
> +++ b/mm/vma_exec.c
> @@ -0,0 +1,92 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Functions explicitly implemented for exec functionality which however are
> + * explicitly VMA-only logic.
> + */
> +
> +#include "vma_internal.h"
> +#include "vma.h"
> +
> +/*
> + * Relocate a VMA downwards by shift bytes. There cannot be any VMAs between
> + * this VMA and its relocated range, which will now reside at [vma->vm_start -
> + * shift, vma->vm_end - shift).
> + *
> + * This function is almost certainly NOT what you want for anything other than
> + * early executable temporary stack relocation.
> + */
> +int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
> +{
> + /*
> + * The process proceeds as follows:
> + *
> + * 1) Use shift to calculate the new vma endpoints.
> + * 2) Extend vma to cover both the old and new ranges. This ensures the
> + * arguments passed to subsequent functions are consistent.
> + * 3) Move vma's page tables to the new range.
> + * 4) Free up any cleared pgd range.
> + * 5) Shrink the vma to cover only the new range.
> + */
> +
> + struct mm_struct *mm = vma->vm_mm;
> + unsigned long old_start = vma->vm_start;
> + unsigned long old_end = vma->vm_end;
> + unsigned long length = old_end - old_start;
> + unsigned long new_start = old_start - shift;
> + unsigned long new_end = old_end - shift;
> + VMA_ITERATOR(vmi, mm, new_start);
> + VMG_STATE(vmg, mm, &vmi, new_start, old_end, 0, vma->vm_pgoff);
> + struct vm_area_struct *next;
> + struct mmu_gather tlb;
> + PAGETABLE_MOVE(pmc, vma, vma, old_start, new_start, length);
> +
> + BUG_ON(new_start > new_end);
> +
> + /*
> + * ensure there are no vmas between where we want to go
> + * and where we are
> + */
> + if (vma != vma_next(&vmi))
> + return -EFAULT;
> +
> + vma_iter_prev_range(&vmi);
> + /*
> + * cover the whole range: [new_start, old_end)
> + */
> + vmg.middle = vma;
> + if (vma_expand(&vmg))
> + return -ENOMEM;
> +
> + /*
> + * move the page tables downwards, on failure we rely on
> + * process cleanup to remove whatever mess we made.
> + */
> + pmc.for_stack = true;
> + if (length != move_page_tables(&pmc))
> + return -ENOMEM;
> +
> + tlb_gather_mmu(&tlb, mm);
> + next = vma_next(&vmi);
> + if (new_end > old_start) {
> + /*
> + * when the old and new regions overlap clear from new_end.
> + */
> + free_pgd_range(&tlb, new_end, old_end, new_end,
> + next ? next->vm_start : USER_PGTABLES_CEILING);
> + } else {
> + /*
> + * otherwise, clean from old_start; this is done to not touch
> + * the address space in [new_end, old_start) some architectures
> + * have constraints on va-space that make this illegal (IA64) -
> + * for the others its just a little faster.
> + */
> + free_pgd_range(&tlb, old_start, old_end, new_end,
> + next ? next->vm_start : USER_PGTABLES_CEILING);
> + }
> + tlb_finish_mmu(&tlb);
> +
> + vma_prev(&vmi);
> + /* Shrink the vma to just the new range */
> + return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
> +}
> diff --git a/tools/testing/vma/Makefile b/tools/testing/vma/Makefile
> index 860fd2311dcc..624040fcf193 100644
> --- a/tools/testing/vma/Makefile
> +++ b/tools/testing/vma/Makefile
> @@ -9,7 +9,7 @@ include ../shared/shared.mk
> OFILES = $(SHARED_OFILES) vma.o maple-shim.o
> TARGETS = vma
>
> -vma.o: vma.c vma_internal.h ../../../mm/vma.c ../../../mm/vma.h
> +vma.o: vma.c vma_internal.h ../../../mm/vma.c ../../../mm/vma_exec.c ../../../mm/vma.h
>
> vma: $(OFILES)
> $(CC) $(CFLAGS) -o $@ $(OFILES) $(LDLIBS)
> diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c
> index 7cfd6e31db10..5832ae5d797d 100644
> --- a/tools/testing/vma/vma.c
> +++ b/tools/testing/vma/vma.c
> @@ -28,6 +28,7 @@ unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
> * Directly import the VMA implementation here. Our vma_internal.h wrapper
> * provides userland-equivalent functionality for everything vma.c uses.
> */
> +#include "../../../mm/vma_exec.c"
> #include "../../../mm/vma.c"
>
> const struct vm_operations_struct vma_dummy_vm_ops;
> diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
> index 572ab2cea763..0df19ca0000a 100644
> --- a/tools/testing/vma/vma_internal.h
> +++ b/tools/testing/vma/vma_internal.h
> @@ -421,6 +421,28 @@ struct vm_unmapped_area_info {
> unsigned long start_gap;
> };
>
> +struct pagetable_move_control {
> + struct vm_area_struct *old; /* Source VMA. */
> + struct vm_area_struct *new; /* Destination VMA. */
> + unsigned long old_addr; /* Address from which the move begins. */
> + unsigned long old_end; /* Exclusive address at which old range ends. */
> + unsigned long new_addr; /* Address to move page tables to. */
> + unsigned long len_in; /* Bytes to remap specified by user. */
> +
> + bool need_rmap_locks; /* Do rmap locks need to be taken? */
> + bool for_stack; /* Is this an early temp stack being moved? */
> +};
> +
> +#define PAGETABLE_MOVE(name, old_, new_, old_addr_, new_addr_, len_) \
> + struct pagetable_move_control name = { \
> + .old = old_, \
> + .new = new_, \
> + .old_addr = old_addr_, \
> + .old_end = (old_addr_) + (len_), \
> + .new_addr = new_addr_, \
> + .len_in = len_, \
> + }
> +
> static inline void vma_iter_invalidate(struct vma_iterator *vmi)
> {
> mas_pause(&vmi->mas);
> @@ -1240,4 +1262,22 @@ static inline int mapping_map_writable(struct address_space *mapping)
> return 0;
> }
>
> +static inline unsigned long move_page_tables(struct pagetable_move_control *pmc)
> +{
> + (void)pmc;
> +
> + return 0;
> +}
> +
> +static inline void free_pgd_range(struct mmu_gather *tlb,
> + unsigned long addr, unsigned long end,
> + unsigned long floor, unsigned long ceiling)
> +{
> + (void)tlb;
> + (void)addr;
> + (void)end;
> + (void)floor;
> + (void)ceiling;
> +}
> +
> #endif /* __MM_VMA_INTERNAL_H */
> --
> 2.49.0
>
